Synthetic quartz glass and process for producing it

Abstract

A synthetic quartz glass for optical use, to be used by irradiation with light within a range of from the ultraviolet region to the vacuum ultraviolet region, which contains fluorine, which has a ratio of the scattering peak intensity of 2250 cm −1 (I 2250 ) to the scattering peak intensity of 800 cm −1 (I 800 ), i.e. I 2250 /I 800 , of at most 1×10 −4 in the laser Raman spectrum, and which has an absorption coefficient of light of 245 nm of at most 2×10 −3 cm −1 .

1. An optical element, to be used by irradiation with light within a range of from the ultraviolet region to the vacuum ultraviolet region, which comprises a synthetic quartz glass containing OH groups and fluorine and having a chlorine concentration of at most 25 ppm, wherein
 the synthetic quartz glass has
 a variation range of an OH group concentration of at most 15 ppm/105 mm, and 
 a variation range of a fluorine concentration of at most 15 ppm/105 mm. 
 
 
     
     
       2. An optical element, to be used by irradiation with light within a range of from the ultraviolet region to the vacuum ultraviolet region, which comprises a synthetic quartz glass containing OH groups and fluorine and having a chlorine concentration of at most 25 ppm, wherein
 the OH groups and the fluorine are distributed in the synthetic quartz glass so that a concentration distribution of the OH groups offsets a concentration distribution of the fluorine; and 
 the synthetic quartz glass has
 a variation range of an OH group concentration of at most 25 ppm/105 mm, and 
 a variation range of a fluorine concentration of at most 25 ppm/105 mm. 
 
 
     
     
       3. The optical element according to  claim 1 , wherein in the synthetic quartz glass the sum of the variation ranges of the fluorine concentration and the OH group concentration is at most 5 ppm/105 mm. 
     
     
       4. The optical element according to any one of  claims 1  to  3 , wherein the synthetic quartz glass has a refractive index variation range (Δn) of at most 10×10 −6 /105 mm. 
     
     
       5. The optical element according to any one of  claims 1  to  3 , wherein the synthetic quartz glass has a refractive index variation range (Δn) of at most 2×10 −6 /105 mm. 
     
     
       6. A method of making an optical element, the method comprising
 doping quartz with fluorine; and 
 producing the optical element of  claim 1 . 
 
     
     
       7. A method of making an optical element, the method comprising
 doping quartz with fluorine; and 
 producing the optical element of  claim 2 . 
 
     
     
       8. The optical element according to  claim 2 , wherein in the synthetic quartz glass the sum of the variation ranges of the fluorine concentration and the OH group concentration is at most 5 ppm/105 mm. 
     
     
       9. The optical element according to  claim 8 , wherein the synthetic quartz glass has a refractive index variation range (Δn) of at most 10×10 −6 /105 mm. 
     
     
       10. The optical element according to  claim 8 , wherein the synthetic quartz glass has a refractive index variation range (Δn) of at most 2×10 −6 /105 mm.